A reason for not allowing static parameters are thread concurrency issues.
An InitialContext is not synchronized against concurrent access. Its likely
that you will encounter problems if you do this. Apart from all other
problems written by Rickard before
Regards
Erik Romson
Steve Roth <[EMAIL PROTECTED]>@JAVA.SUN.COM> on 1999-10-26 20:31:26
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Subject: Re: EJB Restrictions-- threads, io
I looked in the list, but these restrictions seemed to apply to the EJB
Bean
itself. I understand the container-managed instance pooling imposes this
restriction somehow, although I dont understand exactly why.
In particular, I'm wondering if static data can be moved into a utility
class which is created by the EJB bean code, and therefore get around the
static restriction.
Purpose: cache object handle JNDI lookups on bean home interfaces,
transaction mgr, etc.
Since I know these will never change, I'd like to find it once
and
hold onto it.
I have a number of EJBs which will need to call each other.
Rather than
looking up the home interface via JNDI each time I need to call
another bean,
I'd like to cache it.
Something like:
class JNDICache {
private static Context initialContext_;
private static UserTransaction userTransaction_;
static public Context getInitialContext( ) {
if ( initialContext_ == null )
{
Context initialContext= null;
Properties env = System.getProperties();
env.put("java.naming.factory.initial",
"com.sun.jndi.rmi.registry.RegistryContextFactory");
try {
initialContext = new InitialContext(env);
} catch (Exception e) {
System.exit(2);
}
initialContext_= initialContext;
}
return initialContext_;
}
public UserTransaction getUserTransaction( ) {
if ( userTransaction_ == null )
{
UserTransaction utx= null;
try {
Context initialContext = getInitialContext();
utx =
(UserTransaction)initialContext.lookup
("javax.transaction.UserTransaction");
} catch (Exception e) {
System.exit(2);
}
userTransaction_= utx;
}
return userTransaction_;
}
public EJBHome getEJBHome( String beanName ) {
// code to return handle to EJBHome for a given name
// via caching, using JNDI only for first call.
}
}
CODE IN EJB:
-----------
JNDICache jc= new JNDICache();
EJBHome eh= jc.getEJBHome( "BankAccount" ); // nonstatic method,
static
data
EJBObject eo= eh.findByPrimaryKey( ... );
-OR-
EJBHome eh= JNDICache.getEJBHome( "BankAccount" ); // static method,
static data
EJBObject eo= eh.findByPrimaryKey( ... );
Thanks
-Steve Roth, [EMAIL PROTECTED]
> -----Original Message-----
> From: A mailing list for Enterprise JavaBeans development
> [mailto:[EMAIL PROTECTED]]On Behalf Of Rickard �berg
> Sent: Tuesday, October 26, 1999 9:52 AM
> To: [EMAIL PROTECTED]
> Subject: Re: EJB Restrictions-- threads, io
>
>
> Hey
>
> Steve Roth wrote:
> > I forgot to mention the most important restriction I've seen-- no
static
> > methods/data members
> >
> > Can U have static methods/data members?
>
> No. This is strictly fobidden, for good reasons. See archive for
> details: http://archives.java.sun.com/archives/ejb-interest.html
>
> /Rickard
>
> --
> Rickard �berg
>
> @home: +46 13 177937
> Email: [EMAIL PROTECTED]
> Homepage: http://www-und.ida.liu.se/~ricob684
>
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>
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